1. Field of the Invention
Embodiments disclosed herein relate generally to methods of cleaning wellbore. In particular, embodiments disclosed herein relate generally to methods of analyzing wellbore fluids used in cleaning wellbores.
2. Background Art
During the drilling of a wellbore, various fluids are typically used in the well for a variety of functions. The fluids may be circulated through a drill pipe and drill bit into the wellbore, and then may subsequently flow upward through wellbore to the surface. During this circulation, the drilling fluid may act to remove drill cuttings from the bottom of the hole to the surface, to suspend cuttings and weighting material when circulation is interrupted, to control subsurface pressures, to maintain the integrity of the wellbore until the well section is cased and cemented, to isolate the fluids from the formation by providing sufficient hydrostatic pressure to prevent the ingress of formation fluids into the wellbore, to cool and lubricate the drill string and bit, and/or to maximize penetration rate.
One way of protecting the formation is by forming a filter cake on the surface of the subterranean formation. Filter cakes are formed when particles suspended in a wellbore fluid coat and plug the pores in the subterranean formation such that the filter cake prevents or reduce both the loss of fluids into the formation and the influx of fluids present in the formation. A number of ways of forming filter cakes are known in the art, including the use of bridging particles, cuttings created by the drilling process, polymeric additives, and precipitates. Upon completion of drilling, the filter cake may stabilize the wellbore during subsequent completion operations such as placement of a gravel pack in the wellbore.
After any completion operations have been accomplished, removal of filter cake (formed during drilling and/or completion) remaining on the sidewalls of the wellbore may be necessary. Although filter cake formation and use of fluid loss pills are essential to drilling and completion operations, the barriers can be a significant impediment to the production of hydrocarbon or other fluids from the well if, for example, the rock formation is still plugged by the barrier. Because filter cake is compact, it often adheres strongly to the formation and may not be readily or completely flushed out of the formation by fluid action alone.
The problems of efficient well clean-up, stimulation, and completion are a significant issue in all wells, and especially in open-hole horizontal well completions. The productivity of a well is somewhat dependent on effectively and efficiently removing the filter cake while minimizing the potential of water blocking, plugging, or otherwise damaging the natural flow channels of the formation, as well as those of the completion assembly. Further, additional economic efficiency may be realized if operators are able to determine when the well is clean.
Accordingly, there exists a continuing need for developments in wellbore cleaning operations.